Doctoral Dissertation Research: Mesoscale Impacts of Soil Moisture on Convective Precipitation

Texas A&M University, College Station TX

Investigators

Abstract

The goal of this project is to quantify the impact of soil moisture on the location and occurrence of convective precipitation. Although many previous studies have attempted to describe and/or quantify the impact of soil moisture on convective precipitation, none have used observed soil moisture measurements or separated soil moisture-precipitation interactions into the two distinct components (soil moisture-evaporation and evaporation-precipitation). These considerations are necessary to examine the cases in which soil moisture directly influences convective precipitation. The project's three main objectives are: (1) determine if convective precipitation falls preferentially over dry or wet soils, (2) quantify the influence that soil moisture has on low-level atmospheric temperature and humidity, and (3) evaluate how soil moisture spatial gradients influence the probability of convective precipitation. Ground-based radar precipitation will be used to identify mesoscale convective systems. The soil moisture conditions prior to precipitation and the atmospheric humidity and temperature will be determined for each event. The sources of atmospheric moisture will also be determined for each convective event to quantify the proportion of locally- and remotely-sourced moisture. The results of this research will enhance our understanding of land-atmosphere interactions in semi-arid regions around the world. Soil moisture can have an influence on future precipitation. This coupling between the land surface and the atmosphere is important because it provides the basis for improving seasonal climate forecasts. This project will use soil moisture observations in Oklahoma to investigate the physical linkages between soil moisture and precipitation; it is a significant advance since most prior studies have relied on modeled or satellite-based estimates of soil moisture. This project will focus only on localized convective precipitation events since they are hypothesized to be more strongly influenced by soil moisture than large-scale precipitation events (e.g., precipitation events associated with warm fronts and cold fronts). Soil moisture will not simply be correlated with subsequent precipitation, but the physical linkages between soil moisture and the near-surface atmosphere will be examined. The results of this project will enhance our understanding of how soil moisture influences convective precipitation and under what conditions the land surface has the strongest impact on precipitation. The findings of this project will be disseminated to the climate modeling community through conference presentations and publications. It will help improve the accuracy of seasonal climate forecasts since existing climate models do not accurately represent land-atmosphere interactions. An undergraduate researcher assistant will be hired from a diverse group of undergraduate to assist with data collection, processing and analysis. The undergraduate student will receive specialized training in scientific programming and data visualization, and the research will be summarized in an undergraduate thesis and it will be presented at a national scientific meeting.